I did all the Pelions as a 14 year old on a Scripture Union 'Summer Camp' bushwalk. We had 6 days of magnificent cloudless weather and followed an agenda as follows:
Day 1 - Arm River Track to New Pelion, climbing Pillinger along the way.
Day 2 - Abandon packs and climb Pelion West as a day walk. I did this a couple of years ago and the track is quite clear. You can read about it
here.
Day 3 - Up Ewarts Track to camp beside pencil pines below Paddy's Nut. Up Thetis and Paddys Nut after lunch. On the recent Pelion West walk, I spotted the first track marker for Ewarts Track so despite being removed from recent maps, traces of the track have not been completely wiped out.
Day 4 - Day walk sidling around Thetis through intermittent patches of scree and scrub to climb Perins Bluff and Achilies. No tracks but route selection is easy in clear weather.
Day 5 - Shift camp back to New Pelion Hut before breakfast then climb Ossa and Pelion East as a day walk.
Day 6 - Climb Oakleigh before heading out via Arm River Track.
I have since read notes describing a 'Pelion Mountaineering Circuit' where packs are carried in a loop including traverses of Pelion West, Thetis and Ossa. Judging by more recent trips to the 'other' side of these peals, I think it would be quite achievable if you're keen to cart full packs over mountains. You would also need to be good with off track navigation and sensitive about minimal impact bushwalking.
